.\"	$NetBSD: fhopen.2,v 1.17 2009/08/05 23:15:52 wiz Exp $
.\"
.\" Copyright (c) 1999 National Aeronautics & Space Administration
.\" All rights reserved.
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.\" This software was written by William Studenmund of the
.\" Numerical Aerospace Simulation Facility, NASA Ames Research Center.
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.Dd August 5, 2009
.Dt FHOPEN 2
.Os
.Sh NAME
.Nm fhopen ,
.Nm fhstat ,
.Nm fhstatvfs
.Nd access file via file handle
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In sys/types.h
.In sys/mount.h
.Ft int
.Fn fhopen "const void *fhp" "size_t fh_size" "int flags"
.In sys/stat.h
.Ft int
.Fn fhstat "const void *fhp" "size_t fh_size" "struct stat *sb"
.In sys/statvfs.h
.Ft int
.Fn fhstatvfs "const void *fhp" "size_t fh_size" "struct statvfs *buf"
.Ft int
.Fn fhstatvfs1 "const void *fhp" "size_t fh_size" "struct statvfs *buf" "int flags"
.Sh DESCRIPTION
These functions provide a means to access a file given the opaque file handle
.Fa fhp
and the size
.Fa fh_size
of the opaque object as returned by
.Xr getfh 2 .
As this method bypasses directory access restrictions, these calls are
restricted to the superuser.
.Pp
.Fn fhopen
opens the file referenced by
.Fa fhp
for reading and/or writing as specified by the argument
.Fa flags
and returns the file descriptor to the calling process.
The
.Fa flags
are specified by
.Em or Ns 'ing
together the flags used for the
.Xr open 2
call.
All said flags are valid except for
.Dv O_CREAT .
.Pp
.Fn fhstat ,
.Fn fhstatvfs ,
and
.Fn fhstatvfs1
provide the functionality of the
.Xr fstat 2 ,
.Xr fstatvfs 2 ,
and
.Xr fstatvfs1 2
calls except that they return information for the file referred to by
.Fa fhp
rather than an open file.
.Sh RETURN VALUES
Upon successful completion,
.Fn fhopen
returns the file descriptor for the opened file, while
.Fn fhstat ,
.Fn fhstatvfs ,
and
.Fn fhstatvfs1
return 0.
Otherwise, \-1 is returned and
.Va errno
is set to indicate the error.
.Sh ERRORS
In addition to the errors returned by
.Xr open 2 ,
.Xr fstat 2 ,
.Xr fstatvfs 2 ,
and
.Xr fstatvfs1 2 ,
respectively,
.Fn fhopen ,
.Fn fhstat ,
.Fn fhstatvfs ,
and
.Fn fhstatvfs1
will return
.Bl -tag -width Er
.It Bq Er EINVAL
Calling
.Fn fhopen
with
.Dv O_CREAT
set or invalid
.Fa fh_size .
.It Bq Er ESTALE
The file handle
.Fa fhp
is no longer valid.
.El
.Sh SEE ALSO
.Xr fstat 2 ,
.Xr fstatvfs 2 ,
.Xr fstatvfs1 2 ,
.Xr getfh 2 ,
.Xr open 2
.Sh HISTORY
The
.Fn fhopen ,
and
.Fn fhstat
functions first appeared in
.Nx 1.5 .
The
.Fn fhstatvfs
function replaced
.Fn fhstatfs
in
.Nx 3.0 .
